Conserving Seasonal Pans

Seasonal pans occur throughout Malilangwe, especially on alluvial and basalt soils, and they support a remarkable range of temporary aquatic life. Among the most distinctive inhabitants are large branchiopod crustaceans, commonly known as fairy shrimps. Although around 66 species have been recorded in southern Africa, the true diversity is likely to be higher because many areas, including parts of Zimbabwe, remain poorly studied. Research at Malilangwe found seven species of fairy shrimp and one tadpole shrimp in 160 pans across four geological types. Unexpectedly, shrimp diversity showed no clear relationship with geology, suggesting that other ecological processes may play a more important role in shaping where these species occur.

Further research at Malilangwe showed that the eggs of these shrimps can be carried across the landscape by mud-wallowing animals such as elephant, buffalo and rhino. Mud stuck to their bodies can contain dormant eggs, which may later be rubbed off onto vegetation and washed by rain into nearby pans, where the shrimps begin their life cycle again. Because these large mammals move over wide areas, they may help mix shrimp species between pans and across the landscape. This could explain why shrimp diversity does not appear to follow geology alone. It also highlights how closely connected Malilangwe’s ecosystems are: the movement of large mammals can influence the survival of tiny aquatic species, with wider effects on the food webs that depend on them.